We report about a 58-year-old female with coexisting type-I Gaucher's disease (GD) and multiple myeloma (MM). The diagnosis of GD was made in early childhood by means of bone marrow biopsy and was recently confirmed by analysis of the patient's genomic DNA for the underlying glucocerebrosidase mutations and the identification of the 1226G/1448C genotype. At the age of 24 years, the patient developed massive splenomegaly. Therefore, a splenectomy was performed. No further therapy was necessary for the next 34 years until 1999 when progressive anemia and thrombocytopenia occurred. Additional laboratory analysis revealed high serum protein and immunoglobulin (Ig) G levels and evidence of monoclonal gammopathy and lambda light-chain proteinuria, indicating plasma cell dyscrasia. This diagnosis was confirmed by the detection of osteolytic lesions in skeletal X-rays and a bone marrow biopsy showing an extensive infiltration with Gaucher cells and an increase of plasma cells, which expressed lambda light chains. When examined by means of electron microscopy, typical Gaucher cells, i.e., histiocytes containing tubular-structured cytoplasmatic material and spots of plasma cells with an increase of the endoplasmic reticulum, were found. GD associated with acquired MM has been described 13 times in the literature from 1968 to 1997. Only three of the patients were suffering from IgG myeloma. This distribution of the monoclonal component is in contrast to that of patients suffering from MM alone.